1. Field of The Invention
This invention relates to a room temperature vulcanizable organopolysiloxane composition of the dealcohol type. The invention also relates to a method for producing the room temperature vulcanizable organopolysiloxane compound of the above-mentioned type.
2. Description of The Prior Art
As a room temperature vulcanizable organopolysiloxane composition of the dealcohol type, there is known a composition which comprises, as a base polymer, a diorganopolysiloxane which has a hydroxyl group at both ends. The RTV composition further comprises alkoxysilanes in order to block the terminal hydroxyl groups of the molecular chain of the diorganopolysiloxane therewith. This eventually leads to release of alcohols through reaction of the hydroxyl groups with the alkoxysilanes in the composition. However, the released alcohol presents the problem that the shelf life of the composition is considerably impeded. In order to eliminate the alcohol from the composition, it is usual to add scavengers reactive with the alcohol to the composition. The addition of the scavenger compound in turn raises other problems such as of the generation of offensive odor and/or the discoloration of the composition. It will be noted here that the dealcohol-type composition is intended to mean one which makes use of alkoxysilanes as a curing agent and wherein alcohols are released when the composition is cured or vulcanized.
To solve these problems, there have been proposed a number of compositions which comprise, as a base polymer, diorganopolysiloxanes which are blocked with an alkoxy group at both ends thereof. For instance, Japanese Laid-Open Patent Application No. 59-213760 describes a composition which comprises, aside from such a base polymer as mentioned above, a tin compound as a catalyst. Japanese Laid-Open Patent Application No. 61-34063 sets forth a composition which comprises a filler made of a major proportion of an extender filler such as calcium carbonate and a minor proportion of a reinforcing filler to obtain a low modulus type of composition. Moreover, Japanese Laid-Open Patent Application No. 59-213760 describes a composition which comprises a combination of a silane compound having functional groups other than alkoxy groups and an appropriate adhesion improver to improve the adhesiveness.
With high strength RTV organopolysiloxane compositions of the dealcohol type, they have been hitherto prepared by formulating large amounts of various types of reinforcing fillers. However, it has been difficult to impart to the composition a low viscosity and an improved extrusion rate. To cope with the difficulty, it becomes necessary to increase the amounts of ingredients such as a softener, a curing agent and the like. As a consequence, it is not inevitable that the elongation, strength and the like properties be lowered to a significant extent.